Using CPU cooler fan for drawing air away from CPU cooler

obi wan lebo · Post by **obi wan lebo** » Mon Jul 06, 2009 8:46 am

Hello to all. My first post. Hopefully it won't go all wrong.

I have a situation where psu fan is really close to cpu cooler and cpu cooler fan. CPU cooler fan is trying to move the air exactly to opposite direction compared to the PSU fan.

I was wondering that what would happen if I turned the CPU Cooler fan upside down so that it would draw air away from the heatsink instead of pushing air against to the heatsink. I could perhaps also be able to add a case fan next to CPU heatsink. This case fan would draw air directly from outside of the PC case into the PC case and directly towards the CPU heatsink. This would perhaps help cooling half of the CPU cooler heatsink but the other half might suffer because there the most of the cooling would be done by the CPU cooler fan which, as I mentioned, would draw the air away from the CPU heatsink.

In this way the air would move more easily towards PSU fan and the PSU fan probably would spin that quick because the cpu cooler fan and psu fan wouldn't compete against each other?

But, how much would the CPU heatsink temp rise? Should I forget this and try something else?

swivelguy2 · Post by **swivelguy2** » Mon Jul 06, 2009 9:31 am

I think this is a case where a picture would be worth a thousand words.

It sounds like you have a PSU with a bottom-mounted fan pulling air upwards into the PSU, and a tower-style CPU heatsink with the fan blowing downwards through the fins. Is that right?

What is the model of heatsink that you have, and what type of motherboard socket is it mounted to (eg LGA775, AM-2, etc)?

RoGuE · Post by **RoGuE** » Mon Jul 06, 2009 10:25 am

an extremely popular, and proven configuration is a cpu cooler w/fan blowing east to west (west being right out the back of the computer) with the power supply sucking air from the cpu area below it, up into and out the back of the psu.

obi wan lebo · Post by **obi wan lebo** » Mon Jul 06, 2009 1:05 pm

swivelguy2 wrote:I think this is a case where a picture would be worth a thousand words.

It sounds like you have a PSU with a bottom-mounted fan pulling air upwards into the PSU, and a tower-style CPU heatsink with the fan blowing downwards through the fins. Is that right?

Thank you guys for the replys.

Well.. I hate people thinking me as a mindreader by giving too little information about their problems and now I did it for you, guys. Sorry.

Actually the setup is not yet built and I haven't even bought the needed stuff.

PSU does indeed have a bottom-mounted fan pulling air upwards into the PSU.

The cpu cooler heatsink would be right below the psu fan. There isn't much room for the cooler. I think Intel boxed cooler would fit but I am not going to use the boxed one but instead something else.

There isn't room for tower-shaped cooler with fan blowing horisontally. If and when there will be a fan attached to the CPU heatsink it will be blowing air either downwards or upwards.

The case fan I mentioned could be sized like 100x100x10mm (thinking the scythe one) or some silent 120mm fan because there is enough room for the case fan between the pc case and PSU .

The room for the cooler is so small that how low the cooler will be there will be like 2cm (I think 2cm is pretty much the max here) space between the cooler and the cpu. If the cpu fan will be blowing air downwards then what do you guys think that how big issue it is that those two fans are located 2cm from each other and are competing from the same air. Will it cause heating problems too much, more noise etc.?

On the other hand.. If there would be only one option, the option that the cpu cooler fan sitting on the top of the cpu cooler heatsink would draw the air upwards away from the cpu cooler heatsink then would it work as a cpu cooling setup. How much temp rise would this setup cause?

I know Zalman has the new low profile cooler VF2000 (too noisy?) and also the new Big Shuriken might be an option. Then there is the Silverstone low profile product but the heatsink looks a bit too light there and at least the fan should be changed in the Silverstone product, I think. Thermaltake MeOrb is too noisy, I think, and the fan is harder to replace for me there.

I am thinking E5200 or E5300 as a CPU, no overclocking.

swivelguy2 · Post by **swivelguy2** » Mon Jul 06, 2009 1:12 pm

You are probably right in thinking that having two fans right next to eachother (PSU blowing up, CPU blowing down) would be a bad situation.

You could certainly have the CPU fan blow upwards, however that will pump all of the heat from your CPU directly into your PSU, and the PSU will likely ramp up its fan, increasing the noise.

The best option is to find a way to get the CPU heat out the back of the case. You could use a rear case fan blowing outwards and a short homemade duct, if you're comfortable with a little bit of modding. That way all of the heat from the CPU would be trapped inside the duct and expelled from the case.

RoGuE · Post by **RoGuE** » Tue Jul 07, 2009 11:21 am

swivel is right..you really dont want the two fans competing so close together. If you were to do that, it would actually work better to not have a cpu fan at all..which is silly.

if you can't, possibly, at all, never, can get the cpu fan blowing out the back (which I still dont understand), orient the fan to blow up through the cpu cooler and into the psu. Believe it or not, the air coming out of the cpu cooler isn't THAT hot, becasue there is relitively so much of it that it doesn't take on a hot temp. you could probably get away with that, so long as you had fresh room temp air coming in from the front to feed that cpu fan.

-rogue

wharrad · Post by **wharrad** » Tue Jul 07, 2009 4:19 pm

If it helps you at all, I've got a simular problem with an opteron server.

Although I'd never say it's silent, rotating the fan on the CPU reduced temps compared with two working against each other.

So here's an example in practice of it working just fine!

alleycat · Post by **alleycat** » Tue Jul 07, 2009 6:42 pm

There are quite a few examples of exhaust ducting in these forums. Depending on the shape of your heatsink, you should be able to come up with something yourself. Some examples of ducting I have built myself can be found here and here.